CVE-2026-75351 in OpENer
Summary
by MITRE • 10/09/2026
OpENer v2.3/commit 76b95cf, contains an out-of-bounds read in the server-side EtherNet/IP ForwardOpen connection-path parser. This allows a remote attacker to cause a denial of service.
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Analysis
by VulDB Data Team • 10/09/2026
The vulnerability identified in OpENer versions prior to commit 76b95cf represents a critical security flaw within the implementation of the EtherNet/IP protocol stack, specifically affecting the server-side handling of connection requests. OpENer is an open-source library designed for developing devices that communicate using the Common Industrial Protocol (CIP) over Ethernet, widely utilized in industrial automation and control systems to facilitate communication between programmable logic controllers, human-machine interfaces, and other networked equipment. The specific defect resides within the ForwardOpen message parser, which is responsible for establishing a new connection session between an initiator device and the target server. During this process, the parser must validate various parameters included in the request packet, including the connection path that defines how data should be routed through intermediate devices or directly to the endpoint. The flaw arises because the code fails to adequately verify the bounds of memory buffers when processing these connection paths, leading to an out-of-bounds read condition.
From a technical perspective, this vulnerability is classified as CWE-125, which denotes Out-of-Bounds Read. This type of error occurs when software reads data from a memory location that lies outside the intended buffer boundaries. In the context of OpENer, if a remote attacker crafts a malicious EtherNet/IP ForwardOpen request with an improperly formatted or excessively long connection path, the parser may attempt to access memory addresses beyond the allocated space for handling the packet data. While out-of-bounds reads are often associated with information disclosure vulnerabilities where sensitive memory contents can be leaked to the attacker, in this specific instance within OpENer, the primary consequence manifests as a denial of service. The improper memory access likely triggers an exception or causes undefined behavior that results in the termination of the application process or crashes the underlying system running the OpENer library. This effectively renders the industrial device unresponsive and unable to accept further legitimate connections until the service is restarted manually, disrupting operational continuity.
The operational impact of this vulnerability is significant for environments relying on continuous monitoring and control via EtherNet/IP networks. Industrial facilities often depend on real-time data exchange between sensors, actuators, and central controllers. A successful exploitation allows an unauthenticated remote attacker to disrupt these critical processes simply by sending a single malformed packet or repeatedly attempting connections with invalid paths. This aligns with the MITRE ATT&CK technique T1499, Endpoint Denial of Service, where adversaries aim to exhaust resources or crash services rather than steal data. In industrial settings, such disruptions can lead to production halts, safety risks if automated processes are interrupted unexpectedly, and increased maintenance costs due to the need for manual intervention to restore service availability. The lack of authentication requirements in many EtherNet/IP implementations exacerbates this risk, as any device on the same network segment can potentially trigger the crash without needing valid credentials.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary solution is to upgrade OpENer to a version that includes commit 76b95cf or later, which addresses the buffer validation logic in the ForwardOpen parser. Organizations should verify their current software versions against this specific commit hash to ensure they are protected. Additionally, network segmentation plays a crucial role in limiting exposure; by placing industrial control systems on isolated VLANs and restricting access to EtherNet/IP ports using firewalls or intrusion prevention systems, organizations can prevent unauthorized external entities from sending malicious packets directly to the vulnerable devices. Implementing strict input validation at the gateway level before traffic reaches the OpENer instance provides an additional layer of defense against malformed requests. Regular security audits and penetration testing focused on protocol-specific vulnerabilities are also recommended to identify similar weaknesses in other components of the industrial control system infrastructure.